One of the biggest questions SIREN sought to answer was whether individuals who had previously been infected with COVID-19 enjoyed protection from the virus in future. Two groups of participants were studies – those with evidence of a previous COVID-19 infection and those without. When SIREN reported its first analysis, the study showed that 83% of people infected with COVID-19 had some protection against reinfection and this was part of the evidence demonstrating that individuals with a previous COVID-19 infection are likely to be protected against reinfection for several months.
And then vaccines came
As the rollout of vaccines began, the was study rapidly updated to include information about whether the participant had been vaccinated. By expanding the protocol of the study to include vaccine information, SIREN has been able to assess the effectiveness of vaccines. In February 2021, SIREN published findings that healthcare workers were 72% less likely to develop infection after one dose of the vaccine, rising to 86% after the second dose.